This invention relates to a diagnostic tool used to determine degradation of turbine components by pressure measurements in the mid-span packing region between HP and IP sections of the turbine.
Often when conducting a performance validation test on a steam turbine, the flow between the High Pressure (HP) and Intermediate Pressure (IP) sections through the mid-span packing is unknown because it cannot be measured directly. The methods used to determine this flow are very time consuming, require significant cooperation from the customer and their unit operators, and are only completed on units with precision contractual tests, or units that are the subject of characterization tests. Because of these constraints, an assumed value of this flow is used in the majority of performance analyses.
Some units have a provision for performing a blowdown test. To carry out the test, a port is provided through the packing head and shell, with an attached pipe containing an isolation valve and a test section for attaching instrumentation used for measuring temperature, pressure and flow. During normal operation when no test is undertaken, however, the isolation valve is closed, and the test instrumentation is removed.
There remains a need, therefore, for a simple and relatively inexpensive technique for continuously measuring pressure at the mid-span packing region between the HP and IP sections of a steam turbine, so that the gathered pressure can be used as an ongoing diagnostic tool for determining/identifying degradation of various turbine components.